Remove underscore from classes CLDRPluralRule*

Part of program to remove underscores from class names. Checked core and 675
extensions for occurrences. All uses are in core in core are updated in this
patch. There are no uses in Gerrit extensions.

Change-Id: Id3ff16710a11ce1909a83b58505b250736a073e8
Merge "Remove underscore from classes CLDRPluralRule*"